| 摘要 |
Methods for determining a vibratory excitation spectrum are tailored to physical characteristics of a structure having critical elements located thereon to be subjected to vibration testing, such as a PCB to which connectors, resistors, capacitors, inductances, Integrated Circuits (IC) or Ball Grid Array components (BGA) are mounted. The physical characteristics includes a frequency response function corresponding to a testing environment temperature and defined in term of power spectral density amplitude over a global excitation frequency range for the vibratory excitation spectrum and characterized by a plurality of power spectral density amplitude peaks corresponding to a plurality of natural resonance frequencies, each being associated with respective mode shape and damping factor. The method comprises the steps of locating at least one anti-resonance frequency range extending between two main natural resonance frequencies, defining on the basis of the amplitude peaks corresponding to the main natural resonance frequencies at least two corresponding sets of amplitude peaks each including the amplitude peak associated with any other natural resonance frequency near corresponding main natural resonance frequency included in the corresponding set, and defining from the sets of amplitude peaks at least two spectral profile sections associated with corresponding frequency ranges. Each spectral profile section is expressed as power spectral density amplitude according to the mode shape and damping factor associated with corresponding main and other natural resonance frequencies and to the location of said critical elements, to form a vibratory excitation spectrum capable of maximizing vibration power transfer to the critical elements of the structure to be subjected to vibration at the testing environment temperature.
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